The latest version of the CodeIgniter framework has officially been released - version 1.6:

EllisLab is proud to announce the release of CodeIgniter 1.6, our open source web application framework. The release marks a new turn in the development of the framework, and has received considerable attention from both EllisLab developers and the community.

There's lots of new features in this new release including a Database Forge class, improvements to their Active Record implementation, an extendable Model class, and the addition of extendable Helpers.